Since it is generally accepted that microorganisms are the activating agents of dental caries and since dietary fats have been circumstantially implicated as haveing some anticariogenic effects, our proposed research will investigate the role of antimicrobial lipids as potential anticariogenic agents. Our past research has explored basic relationships between lipid structure and their antimicrobial activity. Based on this background, we will elucidate similar structure-function in vitro relationships between lipids and Streptococcus mutans. We will then compare in vitro antimicrobial activity of specific lipids with their effects on the development of dental caries in the several rat model systems. Caries scoring done at Michigan State University for all experimental groups will be periodically checked by other investigators in a double-blind evaluation. Both the kind and levels of antimicrobial lipids in the diet necessary to prevent animal caries will be determined.